package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.annotation.Id;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;
import static com.hmdp.utils.RedisConstants.CACHE_SHOP_KEY;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate string_redis_template) {
        stringRedisTemplate = string_redis_template;
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallBack,
            Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从Redis查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在,直接返回
            return JSONUtil.toBean(json, type);
        }
        // 判断命中的是否是空值
        if (json != null) {
            // 返回一个错误信息
            return null;
        }
        //4.不存在,根据id去数据库查询
        R r = dbFallBack.apply(id);
        //5.数据库里不存在,返回错误
        if (r == null) {
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.数据库里存在,写入Redis
        this.setWithLogicalExpire(key, r, time, unit);
        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R, ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallBack,
            Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从Redis查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否命中
        if (StrUtil.isBlank(json)) {
            //3.未命中,直接返回
            return null;
        }
        //4.命中, 把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        //5.判断是否过期
        LocalDateTime expireTime = redisData.getExpireTime();
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期,直接返回店铺信息
            return r;
        }
        //5.2过期,需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断获取互斥锁是否成功
        if (isLock) {
            //6.3 再次判断缓存是否过期
            json = stringRedisTemplate.opsForValue().get(key);
            if (StrUtil.isNotBlank(json)) {
                redisData = JSONUtil.toBean(json, RedisData.class);
                expireTime = redisData.getExpireTime();
                data = (JSONObject) redisData.getData();
                if (expireTime.isAfter(LocalDateTime.now())) {
                    //缓存已被其他线程更新,直接返回
                    return JSONUtil.toBean(data, type);
                }
            }
            //6.4成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallBack.apply(id);
                    //将数据存入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.5失败,返回过期的商铺信息
        return r;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }


}
